1. Field of the Invention
The present invention pertains to a flexible optical fiber core having an adherent flexible organic polymeric cladding on the outer surface. Specifically, the invention relates to an optical fiber for in vivo use in the tissue of a living mammal wherein the optical fiber has a flexible aliphatic poly(urethane) cladding on the outer surface of the polymeric optical fiber core. The optical fiber core preferably has a refractive index of at least 0.01 greater than the refractive index of the polymeric cladding.
2. Description of the Related Art
Fiber optics have been known for a number of years as described by A. D. Pearson et al. in "Fiber Optics" in the Kirk-Othmer:Encyclopedia of Chemical Technology, 3rd Ed., Vol. 10, John Wiley & Sons, New York, New York, pp. 125-147, published in 1980. Also see A. C. Levy, "Optical Fibers," in the Encyclopedia of Polymer Science and Engineering, H. F. Mark et al (ed.) Vol. 7, pp. 1 to 15, John Wiley and Sons, New York, New York, published in 1986.
S. R. Goldstein, European Pat. No. 073-558-A2 (March 1983) discloses the use of a chemical sensor for pH using a pH sensitive dye with an optical fiber.
S. Kingsley, et al., in FC-7; Fiber Optics Sensors, Chapter 10 "Chemical Sensors", published in 1984 by Information Gate Keepers, 214 Harvard Avenue, Boston, Mass. 02134, discusses the use of a number of sensors for in vitro use.
B. Noethe et al. in U.S. Pat. No. 4,133,915 discloses an optical glass fiber which is first coated with a high boiling optically clear liquid, then coated with a curable resin, such as a urethane.
T. E. Bishop et al. in U.S. Pat. No. 4,472,019 disclose radiation curable coating compositions adapted for application to buffer-coated optical fibers. The new composition comprises (1) from 25 to 70% of a diethylenicterminated polyurethane (which may include urea linkages), where the polyurethane is based on a diisocyanate having an average molecular weight of from 400 to 5000 daltons, (2) from 5% to 40% of a diethylenically unsaturated ester of a diglycidyl ether of a bisphenol having a molecular weight up to about 1000, and (3) from 5 to 30% of a liquid radiation-curable monoethylenically unsaturated monomer having a Tg above about 55.degree.C., especially N-vinyl pyrrolidone. Only glass optical fibers are disclosed.
The above references are incorporated herein in their entirety.
None of these references teach or suggest a current plastic for use as an organic polymeric optical fiber for long-term use in the tissue of a living mammal. An optical fiber for in vivo use in the body area of the beating heart, such as would be required in a heart pacemaker or a defibrillator, needs specific mechanical properties in addition to live tissue/body fluid compatibility. Such a fiber must be capable of being repeatedly deformed in a small bend radius without losing the ability t transmit light. That is, such an optical fiber for use in a moving, beating heart must have tremendous resistance to the development of microbending optical loss. These optical fibers would be useful in any body area for the measurement of various levels of substances or materials in a human body.